Inhibition of calcium signaling in ultraviolet-irradiated fibroblasts: role of tyrosine phosphorylation and protein kinase C. |
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Authors: | S Bagchi G Bhaumik S Raha |
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Affiliation: | Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta, 700064, India. |
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Abstract: | Our aim was to study whether ultraviolet radiation produced any alterations in the subsequent signaling response of V79 fibroblasts to mitogenic stimulus. In ultraviolet C (UVC)-irradiated V79 fibroblasts, increase in cytosolic calcium in response to thrombin was nearly abolished in the presence of 3 mM external Ca(2+). UVC-treated V79 cells showed a greatly enhanced permeability to Ca(2+) which was reversed by pretreatment with genistein, a tyrosine kinase inhibitor. Genistein also alleviated the inhibition of thrombin response caused by UVC. In UVC-treated cells, significant activation of protein kinase C (PKC) occurred only on exposure to 3 mM external calcium and PKC inhibitors (H-7 or staurosporine) reversed UVC-induced adverse effects on the thrombin response. Therefore, it is likely that protein tyrosine phosphorylation by UVC may play a role in the subsequent inhibition of thrombin response in V79 cells through increased calcium influx and activation of PKC. |
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